Control device for electric motors



April 5, 1949. J. L. BOON CONTROL DEVICE FOR ELECTRIC MOTORS 7 FiledSept. 4, 1.942

QJUSEFH L, EDEN INVENTOR ATTORNEYS:

Patented Apr. 5 1949 2,466,364 CONTROL DEVICE FOR ELECTRIC MOTORS.ioseph L. Boon, Rochester, N. 32., assig'nor to Eastman h-IodalrCompany, Rochester, N. 1., a corporation of New Jersey ApplicationSeptember 4, 1942, Serial No. 457,297

2 Claims. 1

The invention relates to control devices, and more particularly tostarting and control devices especially suitable for electric motordrives for high speed cameras.

One object of the invention is the provision of a starting rheostat foran electric motor, and a preset or adjustable stop which may beselectively and manually positioned to limit the movement of therheostat arm to thereby limit or control the speed of the motor to adesired or predetermined point.

Another object of the invention is the provision of an adjustablecontrol which may be selectively positioned to open a switch in themotor circuit to stop the motor after a predetermined time interval.

Still another object of the invention is the provision of an adjustableor preset member for controlling an independent electrical circuit intimed relation to the start of the motor.

A further object of the invention is the provision of controls of theclass above described which are simple in construction, readily, easilyand accurately adjustable, and effective in their operation.

To these and other ends, the invention resides in certain improvementsand combinations of parts, all as will be hereinafter more fullydescribed, the novel features being pointed out in the claims at the endof the specification.

In the drawings:

l is a schematic view of an electric motor and a starting rheostattherefor, showing the arrangement for connecting the rheostat in to themotor, and a limiting stop for the rheostat for controlling the motorspeed;

Fig. 2 is a front view of the rheostat illustrated in Fig. 1, showingthe relation of the movable rheostat arm and the limiting stop therefor;

Fig. 3 control member and the structure by which the controls areconnected to and driven by the motor in a timed relation therewith;

Fig. 4 is a front view of one of the controls il lustrated in Fig. 3,showing the relation of the control cam and the electrical switch whichis operated thereby; and

Fig. 5 shows an external electrical circuit, and the relation thereto ofone of the control membars or cams illustrated in Fig. 3.

Similar reference numerals throughout the various views indicate thesame parts.

The present invention relates to control devices for an electric motorprimarily intended for use in a motion picture camera, particularly ahigh is a sectional view through a modified speed camera of the typeshown in the patent to Tuttle, No. 2,003,973. Although designed for usein such a camera, the controls of the present invention are not intendedto be limited thereto it is contemplated that such motor controlsadapted to a wide variety of uses in which such tor controls arenecessary or desirable. The sent invention is, therefore, to be limitedonly isofar as necessitated by the prior art and the scope of theappended claims. However, as the present invention relates to the motorcontrols per se, the various parts of the camera itself are mitted, asit is believed that a showing of such parts is not necessary to a fullunderstanding of the present invention.

1 snows an electric motor It to which are .ected electric leads or wires52 and [3, the er being, in turn, connected to a main supply l'ie i l.As is well known, a rheostat is often nnected in the circuit of anelectric motor to protect the latter during the starting operationand/or to control the speed of the motor. Such rhecstats are designed sothat when the motor is started, the maximum resistance of the rheor statis in the motor circuit so that the motor speed will be relatively slow.The rheostat arm is then gradually moved to progressively cut outresistances and thereby increase the motor speed, all of which is wellknown in the art and does not need further explanation.

The rhecstat illustrated in the present invention comprises an annularresistance member [5, of well known construction, connected to the motori i by means of the wire 12. The rheostat arm it, on the other hand, isconnected through a wire I! and starting switch id to the other supplyline it. It is now apparent that when the switch is is closed and thearm it is at the position indicated by the numeral 1, Fig. 2, themaximum resistance of the member 15 is in the motor circuit, and themotor will run at its minimum speed. However, the movement of the arm itin a clockwise direction will gradually move the contact 26 thereof overthe resistance element 15 to gradually cut out the resistance andthereby increase the motor speed. The movement of the arm it may bestopped at any point, and the motor speed will then correspond to theposition of the arm. A casing 21 encloses the resistance member 55, andhas inscribed thereon a suitable scale 22 which may designate theresistance cut out or the motor speed, and with which the pointer 23 ofthe arm I 6 will cooperate, as clearly illustrated in Fig. 2.

The rheostat arm 16 may be moved manually,

but it is preferred to operatively connect the arm to the motor H so asto be automatically moved thereby and in timed relation with thestarting thereof. To this end, the arm I6 is secured to one end of ashaft 25, the other end of which has mounted thereon a disk 25 forming apart of a slip clutch, broadly designated by the numeral 21. A seconddisk 28 of the slip clutch is mounted on one end of a shaft 29 andconnected tothe disk 26 through a disk of friction material 38positioned between the two disks 2S and 28, as shown in Fig. l. Thefriction clutch parts may be retained in assembled relation in anysuitable and well-known manner, as for example, as shown in Fig. 3 andto be later more fully described. The other end of the shaft 29 carriesa worm wheel 31 driven by a worm 32 on the motor shaft 33. The lattermay be directly coupled, in a manner not shown, to the film drivesprocket.

It is thus apparent from Fig. 1 that when the starting switch I8 isclosed, the motor II will be energized and the motor shaft 33 will berotated. Such rotation will drive the worm 32, worm wheel 3| and shaft29. Rotation of the latter is transmitted through the slip clutch 21 torotate the shaft 25 as a unit with the shaft 29 to move the rheostat armit in a clockwise direction over the resistance element IE to graduallydecrease the resistance in the motor circuit and thereby increase themotor speed, all of which is well known to those in the art.

The object or objects to be photographed with a high speed camera movevery rapidly, or the operation or time duration thereof is exceedinglybrief so that in order to secure accurate and satisfactory photographicrecords the drive motor should be at a definite speed, or at least abovea minimum desired speed before the exposure is made. This desired speedcan be secured by limiting or arresting the movement of the rheostat arm[6 when the latter reaches a proper or desired position, as indicated bythe scale 2|. However, as this minimum desired speed varies withconditions and with the subjects being photographed, the final positionof the arm It along the scale 21 will correspondingly var to provide thedesired or required motor speed.

In order to secure such variable speed control,

the present invention provides a movable or adjustable stop adapted tobe positioned in the path of the rheostat arm It or the pointer 23thereof to arrest the movement of the arm It to thus limit the amount orresistance which is cut out of the motor circuit and thus control themotor speed. 4

This stop comprises, in the present embodiment, an L-shaped member, onearm 35 of which is loosely mounted on the shaft 25 to project radiallytherefrom and to overlie the scale 2| with which it cooperates toindicate the setting of the stop. The other arm 36 of the stop memberoverlies the outer surface of the casing 2|, as best shown in Fig. l.The stop member is thus freely movable about the shaft 25 and over thescale 2! and may be readily and easily adjusted to the desired positionrelative thereto to assure the desired minimum motor speed. When thestop is properly adjusted, it may be locked or secured in adjustedposition in any suitable and well-known manner, as for example, by alocking member 31 arranged to be screwed or clamped down to draw the arm36 of the stop member into clamping engagement with the outer surface 38of the casing 2|. The stop may thus be moved and securely retained inany desired position of adjustment.

It is now apparent that when the rheostat arm i6 is moved, in a mannerabove described, the re sistance of the motor circuit will be graduallydecreased and the motor speed will accordingly increase. However, uponengagement of the arm it with the stop member 35, the arm I6 is heldpositively against further movement to limit the amount of resistancecut out of the motor circuit to thus secure the desired or minimum motorspeed. Of course, a slight lag may occur between the engagement of therheostat arm IS with the stop and the attainment of motor speedcorresponding to the stop setting or adjustment, as is well known.Furthermore, the engagement of the rheostat arm It with the stop willlimit further rotation of the arm [6 of the shaft 25, but as the shaft29 is being continually rotated by the motor II, a slippage occurs inthe slip clutch 21 to permit the required relative movement between theclutch disk 26 and 28, as will be readily apparent.

By means of the above arrangement, the motor is started up upon closingthe starting switch it, and the motor will then be gradually brought upto substantially the desired or minimum required speed, whereupon therheostat arm It will engage the stop member 35 to limit further movementof the rheostat arm to thus retain the motor at or above the desiredminimum speed. After the film strip has been run through the camera, theswitch 18 may be opened to break the motor circuit to stop the motor Ii. It is preferred, however, to provide a means whereby the motorcircuit is automatically opened when the film supply is exhausted orafter a predetermined length of film has been run through the camera.

To secure this result, a second switch, preferably a micro switch 45, isarranged in the circuit of the motor I l and in series with the start-.ing switch It, in a manner not shown but believed to be readilyapparent to those in the art. The switch is of the normally closed typeand is provided with a protruding pin or button 46 which extends througha portion 41 of the front wall of the camera body and into a recess 48formed therein. A switch opening or control member in the form of a cam49 is rotatably mounted in the recess 48, in a manner to be laterdescribed, and is provided with a portion 50 adapted to engage and movethe button 46 to open the switch 45 to stop the motor. The cam 49 isaccessible from the front of the camera and may be manually rotated toactuate the switch 45, but it is preferred to operatively connect thecam to the motor 1 I so that the opening of the switch will be in timedrelation to the movement of the film through the camera or to thestarting of the motor.

To secure this result, the motor I i is connected by means of a beltdrive, not shown, to a pulley 5i mounted on a shaft 52 which carries aworm 53 adapted to engage and drive a worm wheel 54 secured to one endof a control shaft 55. The shaft 53 may be connected, in any suitablemanner, to the film take-up spool or reel to drive the latter. The shaft55 is supported in spaced bearings 5% formed in the camera body, and hassecured to the opposite end thereof a pinion 51 which meshes with a gear58 secured to the inner end of the cam carrying shaft 59. The latterextends through a bushing or sleeve 60 positioned in a portion GI of thefront wall of the camera. and projects into the recess 48 to receive aknob 62 formed with an annular flange 53 to which the cam 49 is securedby screws, or other suitable .66 of the knob 52.

vabove described. =operatively connect the rheostat arm it to the shaft.55 so as to be driven thereby. It will be fastening means, all asclearly shown in Fig. 3. The shaft 59 is thus driven by the motor H and:in timed relation therewith. The cam supporting knob E2 is adjustablyconnected to the shaft 59, in a manner to be later described, so thatthe knob and cam may be rotated relative to the shaft to initiallyadjust or set the cam so that the latter will actuate the switch 45 in atimed re lation to the movement of the film strip through the camera orthe starting of the motor i I.

The cam knob 62 is preferably adjustably mounted on the shaft 59 so thatit may be ro-- .tated relative thereto to adjust or set the cam 49 tooperate the switch '45 at a predetermined time. For example, if a filmroll of 100 feet is used in the camera, the cam 49 and knob 52 may beset as a unit so that when the 100 feet had .62 on the shaft 59 which isprovided with a flange or collar 85 spaced from the rear face A bowedannular spring ti surrounds the shaft 59 and is positioned intermediatethe collar 55 and the face 6% of the knob '62 and tends to force thelatter to the left,

as viewed in Fig. 3. A screw 68 is threaded into the end of the shaft 59and has a head as thereof in engagement with the recessed face it of theknob 62 to hold the latter in axial position on the shaft .59, asclearly shown in Fig. 3. The

flange 65, the spring 67, and the screw 53 with its head 69 provide afriction connection and driving means between the knob 62 and the shaft,59. By means of this arrangement, the knob will be driven asa unit withthe shaft 59. However, the knob 52 and cam 4@ may be rotated relative tothe shaft .59 to initially set or adjust the cam 49. The scale ll formedon the front camera wall cooperates with an indicating mark on the cam49, such as the mark 72, to facilitate the initial setting or adjustmentof the cam.

With the arrangements shown in Fig. 3, the rheostat, illustrated in Fig.1, may be driven by themotor II in the manner shown in Fig. 1 and It ispreferred, however, to

apparent that in this arrangement, the rheostat arm will also be drivenby the motor ii and in timed relation therewith. In this modified drive,of the rheostat arm, a shaft is rotatably mounted in a sleeve 76carried by a plate "ill and has mounted on one end thereof a bevel gear13 which meshes with a bevel gear 'li carried by the shaft 55. The otherend of the shaft 15 has formed thereon a disk 89 of a slip clutchbroadly designated as 8i which may be of the same construction as thatillustrated in 1, and above described. A second disk 82 of the slipclutch is spaced from and connected to the disk 80 by a plate 83 offriction material. The clutch parts are retained in assembled relationby U springs 84, each of which has one leg 85 thereof secured oranchored to the face 85 of the disk 88 by suitable fastening means, anda free leg 81' which yieldably engages the exposed face of the disk 82to Press the latter towards the disk 80 to provide a frictional drivingcon nection therewith. The disk 32 is formed on the end of a shaft 89which may be suitably connected to the rheostat arm [6 to rotate thelatter in the same manner as the shaft 25 above described.

Sometimes, it is desirable to photographically record the operation ofan electrical device arranged in an electrical circuit which ispositioned externally of the camera and independent of the circuit ofthe motor ii. Fig. 5 is a schematic example of such an arrangement inwhich a lamp 9!, such as a photoflash lamp, is connected by wires 92,93, and 9G and switch :95 to a suitable source of electrical energyindependent of the motor circuit. It is apparent that when the switch isclosed, the lamp $55 will be energized. As is well known, the flash ofsuch lamp is ex- (3'; dingly brief, being only a few thousandths of asecond. With such a short time duration, it is essential to the securingof accurate and satisfactory photographic records of the flash that themotor should attain the desired speed, or at least be above a minimumrequired speed before switch 9%"; is closed to flash the lamp 9|. Forthis reason, the closing of the switch '95 is preferably controlled fromthe motor Ii so as to be actuated in timed relation therewith. Forexample, it may be desirable to delay the closing of the switch untilsay feet of film had been run through the camera thus assuring that themotor has attained the desired speed when the flash is recorded.

To secure this result, the switch 95, Which is also preferably a microswitch similar to switch mounted in the camera body so that an operatingbutton Q6 thereof projects through a wall ill of the camera and into arecess 98 arranged adjacent the recess 38 of the cam 49, as clearlyshown in Fig. 3. The switch is connected to terminals of a p1ug-insocket, not shown, mounted on the camera body and to which the lines 93and 9 may be connected to insert the switch in series therewith, .asschematically illustrated in Fig. 5. The closing of the switch d5 may becontrolled by a cam 19' shown in Fig. 5. As the structure and drivingarrangements for the cams ill and ill are duplicates, the detaileddescription relating thereto need not be repeated, and correspondingparts will be designated by the same numerals except those relatingspecifically to cam 28' will be differentiated by the addition of aprime to the various numerals, as will be apparent from Fig. 3. The camlike cam 39, may be initially adjusted so the operating portion Sillthereof will not engage the button tfi of the switch 95 until apredetermined length of film has been run through the camera, or untii apredetermined time interval has elapsed after the closing of thestarting switch it. A. suitable scale and mark, not shown, similar tothe scale ii and mark 12, may be provided for initially adjusting thecam 69.

Thus each cam 4-9 and id is operatively connected to and driven by themotor i l and in timed relation therewith. However, each cam may beseparately and independently selectively adiusted to actuate the switchassociated therewith in a predetermined relation to the actuation of theother switch, or the movement of the film strip. Obviously, the cam 49will be set to trip or close the switch 95 prior to the opening of theswitch 55 by the cam 39. However, if no external circuit, such as thatshown in Fig. 5 is connected to switch 95, the latter will beinoperative and only the switch 45 will be opened by the cam 49 inaccordance with the initial setting or adjustment of the latter.

The operation of the structure illustrated in Fig. 3 may be brieflysummarized as follows:

With high speed cameras, the object or subject being photographed eithermoves quite rapidly or has a very short interval of operation, oftenbeing not more than a few thousandths of a second, as in the case of thefiash of a lamp, such as the lamp 9|. In order to secure accuratephotographic records of such subjects, it is essential that the drivemotor attain, or at least be above, a desired minimum speed before theexposure is made. For this reason, the cam 49 is manually adjusted so asto trip or close the switch 95 to momentarily energize the lamp 9! aftersay 75 feet of film has been run through the camera. This delay of 75feet will insure that the motor and film are at the required speed toaccurately record the fiash of the lamp 9! before the switch 95 isclosed. If a IOU-foot roll or reel of film is used, the cam 49 is thenset or adjusted to open the switch 45 after 100 feet have been run.Obviously if a film of a dilferent length is used, the cam 49 isadjusted to correspond to such length so as to trip the switch 45 whenthe film supply is exhausted. Thus the cams 49 and 49 are initiallyadjusted or preset in a predetermined relation and prior to the closingof the starting switch I8. The latter is then closed to start the motorH which, through the belt drive, pulley i, worm and worm wheel 53 and54, drives the rheostat arm i6 until the latter engages the adjustedstop arm to control the motor speed. Rotation of the shaft 55 alsorotates the pinion 57 to simultaneously and uniformly drive the equalsized gears 58 and 59' at the same speed and in timed relation to themotor H. The gears 58 and 58 in turn, drive the shafts 59 and 59 onwhich the cam knobs 62 and 62' are frictionally mounted. The cams 49 and49 are thus driven at the same speed by the motor H and in timedrelation therewith. When the motor has been run for a time interval inaccordance with the initial setting of the cam 49, the portion 50 of thelatter then engages the button 96 to operate the switch 95 to close thelatter to momentarily energize the lamp 9!. Of course, if this externalcircuit is not used, the cam 49 need not be set and may be disregarded.The motor continues to rotate the cams 49 and 49 until a time intervalhas elapsed corresponding to the adjustment of the cam 49. Whereupon,the switch is opened to break the motor circuit to stop the motor.

The present invention thus provides controls which are driven by andoperated in timed relation to the starting of the motor, or the movementof a film strip through the camera. Certain of the controls may beinitially adjusted or preset so as to control certain operations inpredetermined timed relations.

While one embodiment of the invention has been disclosed, it is to beunderstood that the inventive idea may be carried out in a number ofways. This application is, therefore, not to be limited to the precisedetails described, but is intended to cover all variations andmodifications thereof falling within the scope of the appended claims.

I claim:

1. In a control device for a high speed camera, the combination with anelectric motor, of a rheostat connected in the circuit of said motor tocontrol the speed thereof, means including a slip clutch for operativelyconnecting said rheostat to said motor so as to be driven thereby and intimed relation therewith, an adjustable stop for limiting the movementof said rheostat to selectively control the speed of said motor, aswitch in the circuit of said motor, an adjustable time control memberfor said switch, and means for operatively connecting said controlmember to said motor to be operated thereby to open said switch to stopsaid motor in accordance with the time adjustment of said controlmember.

2. In a control device for a high speed camera, the combination with anelectric motor, of a rheostat connected in the circuit of said motor andprovided with a movable arm for adjusting said rheostat to control thespeed of motor, means for operatively connecting said arm to said motorto be driven thereby and in timed relation therewith, a stop membermovable to a predetermined position in the path of said arm to limit themovement of the latter to selectively control the speed of said motor, aswitch arranged in the circuit of said motor, an adjustable controlmember, means for operatively connecting said control member to saidmotor to be driven thereby, and an actuating portion on said controladapted to engage and open said switch to stop said motor after a timeinterval determined by the adjustment of said control member.

JOSEPH L. BOON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

